In recent years, environmental pollution problem by organic chlorinated compounds such as TCE (trichloroethylene), PCE (tetrachloroethylene), dichloro-methane, PCS (polychlorinated biphenyl) and dioxins is a big problem, and a treating agent for detoxification to soils, wastewater, groundwater and the like polluted by those organic chlorinated compounds, and its treatment method is investigated.
For example, a technique of reduction dechlorinating polluted wastewater and service water with an Fe powder or an Fe powder chemically plated with Ni or Cu is reported (for example, Non-Patent Document 1). However, dissolved oxygen in polluted wastewater and service water is required to remove in order to suppress performance deterioration with the lapse of time of such treating agents themselves. Further, the effect was not obtained unless the range of nickel plating amount showing activity is large.
In the case of a treatment method of polluted soils, sludge, sewage and the like, a method of treatment by adding an iron series treating agent containing carbon to polluted soils of a limited range (for example, Patent Document 1), and a treatment method of using an metal series treating agent comprising a combination of Fe with Ni, Cu and carbon (for example, Patent Documents 2 and 3) are reported particularly as a chemical treatment. However, it was not said that decomposition ability is sufficient.
Other than the above, decomposition of organic chlorinated compounds by a metal series treating agent comprising a combination of Fe with a different kind of elements is reported (for example, Patent Documents 4 and 5). However, in a high-active iron powder having a large proportion of fine particles of 50 μm or less by the method of strong pulverization, there was the problem in safety such as ignition. Further, in fine and high-active iron powder, it is difficult to uniformly mix the same with a solid material such as a soil, and sufficient decomposition performance was not exhibited.
Heretofore, an iron powder for decomposition of organic chlorinated compounds, containing Ni and carbon has been known. However, decomposition rate in soils was low, and a long time was required for the decomposition of sparingly-decomposable PCE. In order to improve those performances, it was necessary to increase the Ni content (Patent Documents 6 to 12).
[Non-Patent Document 1] Senzaki et al., Kogyo Yosui, Vol. 391, (1991), 29
[Patent Document 1] JP-A-11-235577
[Patent Document 2] JP-A-2000-5740
[Patent Document 3] JP-A-2002-20806
[Patent Document 4] JP-A-2003-80220
[Patent Document 5] JP-A-2003-136051
[Patent Document 6] JP-A-2003-105313
[Patent Document 7] JP-A-2004-57881
[Patent Document 8] JP-A-2004-305235
[Patent Document 9] JP-A-2004-305792
[Patent Document 10] JP-A-2005-95750
[Patent Document 11] JP-A-2005-34696
[Patent Document 12] JP-A-2005-118755
As the conventional agent which detoxifies soils, industrial wastes, sewage, sludge, wastewater, groundwater and the like polluted by organic chlorinated compounds, iron series decomposing agents containing different kinds of elements such as Ni and carbon are known. However, iron series decomposing agents that can decompose and clean the organic chlorinated compound faster than those decomposing agents were required. Particularly, in the conventional agents having activity increased by fine particles, it is difficult to disperse in the case of using the same in solid materials such as soils, and as a result, sufficient decomposition properties are not obtained. Further, there was the danger of ignition.
Further, in the conventional iron powder for decomposition of organic chlorinated compounds, it is necessary to increase Ni content in order to improve decomposition ability. Thus, an iron powder for decomposition of organic chlorinated compounds, having high treatment ability for cleaning soils and containing less Ni content was demanded.